Tortiose vs Hare Comparison

[mark7331]

Tonight was the first chance I've had to grab a few subs between clouds with my new OO SPX F4.5. So I decided to do a comparison test between the newer, faster, scope and my original, slower NexStar 6SE. I'd been getting very poor results with the 6SE even with 5 minute subs. They seemed to contain more noise than data .

I took a 15sec unguided sub of M27 with a Clear IR block filter and offered it up against one I'd taken with the NexStar 6SE at F10. I've rotated the 6SE image so it has the same orientation as the SPX image. Both images are straight from the CCD, converted to jpeg with the same visualisation. Apart from resizing both images to the same dimensions no other conversions or tampering of any kind have been made.

Apart from the OTAs I've used exactly the same gear - CCD, mount etc. The image scale difference is due to focal length - 1500mm 6SE vs 900mm SPX.

The 6SE image is very grainy and contains far less data. I guess this is expected but I've been blown away at the huge difference. I also managed 8 x 5min autoguided subs before the clouds ganged up on me. The difference is totally amazing. The autoguiding also was a great deal smoother even though there was mist (probably because I wasn't trying to guide an SCT).

So it seems that the Hare does indeed beat the Tortiose where imaging is concerned!

[yeti monster]

Interesting and encouraging, for someone like me, who has yet to fall down the slippery slope.

[Sparrow]

No surprise there but nice to see it demonstrated:). As much as I loved my 6SE, I knew at F10 it would be too slow for serious DSO work which is why I moved on to my 8" newt F5. I'm yet to acquire and read the book "Make evry photon count", but the title of the book really does sum it up.

[dph1nm]

Why is the background so much higher on the 6SE shot?

NigelM

[mark7331]

Why is the background so much higher on the 6SE shot?

NigelM

To answer this I've attached the histograms from the two shots. You can see that the SPX has much, much more data and the noise signature is the little bump to the left of its histogram - in the range of 200-300 ish ADU. That's all that the 6SE data is comprised of - mostly noise and hardly any signal. So the 6SE looks lighter because the standard visualisation of AstroArt tries to show you something and in this case all it has to work with is noise.

The SPX image on the other hand has lots of data (thankfully!)

Mark